1. Field of the Invention
The present invention relates to injector nozzles for injection molding machines, and in particular to multi-orifice injector nozzles for the simultaneous injection of material through a plurality of injection channels into an injection mold.
2. Description of the Prior Art
Multi-orifice injector nozzles have been known for some time in conjunction with injection molding machines. One such device is disclosed in my copending prior application Ser. No. 259,279, now U.S. Pat. No. 3,820,930. There, I have disclosed a three-orifice injector nozzle in which the orifices are interconnected within the body of the injector head by branch channels which start from the main channel at right angles, and lead into three parallel nozzle inserts via right-angle junctions.
A peculiar problem was encountered with this type of multi-orifice injector nozzle in connection with thermoplastic materials which are very sensitive to changes in temperature. This is the case, for example, with the polymerization products of vinyl chloride which are moldable successfully only within a rather narrow temperature range. Thus, it was found that, when clear plastic material such as hard polyvinyl chloride is molded, visible impurities becomes embedded in the finished molded part. These impurities have been found to be thermally decomposed plastic particles.